To provide references for the design of injectors in the combustion-driven continuous wave DF/HF chemical laser, five injectors of different structure were calibrated on flow rate by original criterion (mass-time method). Moreover, the results were explained reasonably by boundary-layer theory. The results show that the flow coefficient increases with the increase of the inlet pressure, and varies from 0.677 to 0.772. At the same condition of inlet pressure, the flow coefficient increases with the diameter and decreases with the length of the orifice. The flow coefficient of the slanting orifice is slightly smaller than the normal one with the same dimension.